448 research outputs found
Snipers, Shills, and Sharks eBay and Human Behavior
Every day on eBay, millions of people buy and sell a vast array of goods, from rare collectibles and antiques to used cars and celebrity memorabilia. The internet auction site is remarkably easy to use, which accounts in part for its huge popularity. But how does eBay really work, and how does it compare to other kinds of auctions? These are questions that led Ken Steiglitz--computer scientist, collector of ancient coins, and a regular eBay user--to examine the site through the revealing lens of auction theory. The result is this book, in which Steiglitz shows us how human behaviors in open markets like eBay can be substantially more complex than those predicted by standard economic theory. In these pages we meet the sniper who outbids you in an auction's closing seconds, the early bidder who treats eBay as if it were an old-fashioned outcry auction, the shill who bids in league with the seller to artificially inflate the price--and other characters as well. Steiglitz guides readers through the fascinating history of auctions, how they functioned in the past and how they work today in online venues like eBay. Drawing on cutting-edge economics as well as his own stories from eBay, he reveals practical auction strategies and introduces readers to the fundamentals of auction theory and the mathematics behind eBay. Complete with exercises and a detailed appendix, this book is a must for sophisticated users of online auctions, and essential reading for students seeking an accessible introduction to the study of auction theory.eBay, auctions, auction theory, human behavior, open markets, strategies, English auctions, Vickrey auctions
Frugality in path auctions
We consider the problem of picking (buying) an inexpensive path in a graph where edges are owned by independent (selfish) agents, and the cost of an edge is known to its owner only. We study the problem of finding frugal mechanisms for this task, i.e. we investigate the payments the buyer must make in order to buy a path. First, we show that any mechanism with (weakly) dominant strategies (or, equivalently, any truthful mechanism) for the agents can force the buyer to make very large payments. Namely, for every such mechanism, the buyer can be forced to pay , where is the cost of the shortest path, is the cost of the second-shortest path, and is the number of edges in . This extends the previous work of Archer and Tardos}, who showed a similar lower bound for a subclass of truthful mechanisms called min-function mechanisms. Our lower bounds have no such limitations on the mechanism. Motivated by this lower bound, we study mechanisms for this problem providing Bayes-Nash equilibrium strategies for the agents. In this class, we identify the optimal mechanism with regard to total payment. We then demonstrate a separation in terms of average overpayments between the classical VCG mechanism and the optimal mechanism showing that under various natural distributions of edge costs, the optimal mechanism pays at most logarithmic factor more than the actual cost, whereas VCG pays times the actual cost. On the other hand, we also show that the optimal mechanism does incur at least a constant factor overpayment in natural distributions of edge costs. Since our mechanism is optimal, this gives a lower bound on all mechanisms with Bayes-Nash equilibria
Upper Bound on the Products of Particle Interactions in Cellular Automata
Particle-like objects are observed to propagate and interact in many
spatially extended dynamical systems. For one of the simplest classes of such
systems, one-dimensional cellular automata, we establish a rigorous upper bound
on the number of distinct products that these interactions can generate. The
upper bound is controlled by the structural complexity of the interacting
particles---a quantity which is defined here and which measures the amount of
spatio-temporal information that a particle stores. Along the way we establish
a number of properties of domains and particles that follow from the
computational mechanics analysis of cellular automata; thereby elucidating why
that approach is of general utility. The upper bound is tested against several
relatively complex domain-particle cellular automata and found to be tight.Comment: 17 pages, 12 figures, 3 tables,
http://www.santafe.edu/projects/CompMech/papers/ub.html V2: References and
accompanying text modified, to comply with legal demands arising from
on-going intellectual property litigation among third parties. V3: Accepted
for publication in Physica D. References added and other small changes made
per referee suggestion
Exact soliton solutions of coupled nonlinear Schr\"odinger equations: Shape changing collisions, logic gates and partially coherent solitons
The novel dynamical features underlying soliton interactions in coupled
nonlinear Schr{\"o}dinger equations, which model multimode wave propagation
under varied physical situations in nonlinear optics, are studied. In this
paper, by explicitly constructing multisoliton solutions (upto four-soliton
solutions) for two coupled and arbitrary -coupled nonlinear Schr{\"o}dinger
equations using the Hirota bilinearization method, we bring out clearly the
various features underlying the fascinating shape changing (intensity
redistribution) collisions of solitons, including changes in amplitudes, phases
and relative separation distances, and the very many possibilities of energy
redistributions among the modes of solitons. However in this multisoliton
collision process the pair-wise collision nature is shown to be preserved in
spite of the changes in the amplitudes and phases of the solitons. Detailed
asymptotic analysis also shows that when solitons undergo multiple collisions,
there exists the exciting possibility of shape restoration of atleast one
soliton during interactions of more than two solitons represented by three and
higher order soliton solutions. From application point of view, we have shown
from the asymptotic expressions how the amplitude (intensity) redistribution
can be written as a generalized linear fractional transformation for the
-component case. Also we indicate how the multisolitons can be reinterpreted
as various logic gates for suitable choices of the soliton parameters, leading
to possible multistate logic. In addition, we point out that the various
recently studied partially coherent solitons are just special cases of the
bright soliton solutions exhibiting shape changing collisions, thereby
explaining their variable profile and shape variation in collision process.Comment: 50 Pages, 13 .jpg figures. To appear in PR
A Taylor-Couette Dynamo
Recent experiments have shown that it is possible to study a fundamental
astrophysical process such as dynamo action in controlled laboratory conditions
using simple MHD flows. In this paper we explore the possibility that
Taylor-Couette flow, already proposed as a model of the magneto-rotational
instability of accretion discs, can sustain generation of magnetic field.
Firstly, by solving the kinematic dynamo problem, we identify the region of
parameter space where the magnetic field's growth rate is higher. Secondly, by
solving simultaneously the coupled nonlinear equations which govern velocity
field and magnetic field, we find a self-consistent nonlinearly saturated
dynamo.Comment: 5 pages, 11 figures. To appear in Astron. Astrophy
User-Centred Design Actions for Lightweight Evaluation of an Interactive Machine Learning Toolkit
Machine learning offers great potential to developers and end users in the creative industries. For example, it can support new sensor-based interactions, procedural content generation and end-user product customisation. However, designing machine learning toolkits for adoption by creative developers is still a nascent effort. This work focuses on the application of user-centred design with creative end-user developers for informing the design of an interactive machine learning toolkit. We introduce a framework for user-centred design actions that we developed within the context of an EU innovation project, RAPID-MIX. We illustrate the application of the framework with two actions for lightweight formative evaluation of our toolkit—the JUCE Machine Learning Hackathon and the RAPID-MIX API workshop at eNTERFACE’17. We describe how we used these actions to uncover conceptual and technical limitations. We also discuss how these actions provided us with a better understanding of users, helped us to refine the scope of the design space, and informed improvements to the toolkit. We conclude with a reflection about the knowledge we obtained from applying user-centred design to creative technology, in the context of an innovation project in the creative industries
- …